A new study finds that these effects are indeed real and rooted in brain activity. And this isn’t with just people suffering from depression but also bipolar disorder. The study in fact discovers that what we thought were two unrelated mood disorders are in fact more similar than we realise, lending credence to a theory that mood disorders may lie along a spectrum, rather than comprise distinctly unrelated diagnoses.
For the study, published in the journal Brain, cognitive tests on 612 women were conducted. Two-thirds of the participants suffered from major depression or bipolar disorder, while the rest suffered from no such disorder. The test measured control over cognitive functions like attention and working memory, and the women were asked to react quickly when certain letters were flashed on a screen amid other random letters.
The researchers found that women who suffered from depression and bipolar disorder performed poorly compared to those who were mentally healthy. As a separate part of the experiment, researchers also put 52 women under a brain scanner while the tests were in progress. Women with depression or bipolar disorder had different levels of cognitive activity in an area of the brain that controls important functions like attention, working memory, problem solving and reasoning. The women with bipolar disorder were found to have lower than normal activity in this part of the brain.
The varying activity in the same area of the brain suggests a continuum, showing that these two conditions may not be two distinct disorders but lie along the same spectrum. According to neuro psychologist Kelly Ryan, lead author of the study, “Traditionally, in psychiatry, we look at a specific diagnosis, or category. But the neurobiology is not categorical—we’re not finding huge differences between what clinicians see as categories of disease. This raises questions about traditional diagnoses.”